WBJEE · Physics

Mechanics, waves and electricity

50 practice questions, each with the answer and an explanation.

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Random questions from this topic, one at a time. You see the answer and the explanation straight after each one.

All 50 questions

  1. What force gives a mass of 9 kg an acceleration of 9 m/s²?
  2. What is the kinetic energy of a 20 kg body moving at 4 m/s?
  3. How much gravitational potential energy does a 2 kg mass gain when lifted 11 m? (take g = 10 m/s²)
  4. A machine takes in 800 J of energy and gives out 600 J of useful work. What is its efficiency?
  5. What is the pressure due to a column of liquid of density 800 kg/m³ and depth 10 m? (take g = 10 m/s²)
  6. A resistor of 2 Ω carries a current of 5 A. What is the potential difference across it?
  7. How much energy in kWh does a 500 W heater use in 4 hours?
  8. A gas in a rigid container is at 100 kPa and 400 K. Its temperature is changed to 600 K. What is the new pressure?
  9. A body moves in a circle of radius 20 m at 30 m/s. What is its centripetal acceleration?
  10. A body of volume 0.001 m³ is fully immersed in a liquid of density 1000 kg/m³. What is the upthrust? (take g = 10 m/s²)
  11. A 2 kg trolley moving at 10 m/s hits a stationary 3 kg trolley and they stick together. What is their common speed?
  12. A body moving at 3 m/s accelerates uniformly at 8 m/s² for 7 s. What is its final speed?
  13. What force gives a mass of 19 kg an acceleration of 5 m/s²?
  14. How much gravitational potential energy does a 3 kg mass gain when lifted 8 m? (take g = 10 m/s²)
  15. What is the pressure due to a column of liquid of density 1030 kg/m³ and depth 20 m? (take g = 10 m/s²)
  16. How much energy in kWh does a 1000 W heater use in 2 hours?
  17. A wire 0.2 m long carries 2 A at right angles to a magnetic field of 0.2 T. What force acts on it?
  18. A transformer has 1000 turns on the primary coil and 20000 turns on the secondary. The primary voltage is 220 V. What is the secondary voltage?
  19. How much heat is needed to warm 0.5 kg of water by 40 °C? (specific heat capacity of water = 4200 J/(kg °C))
  20. An object is placed 20 cm from a convex lens of focal length 10 cm. How far from the lens is the image?
  21. A body of volume 0.005 m³ is fully immersed in a liquid of density 1200 kg/m³. What is the upthrust? (take g = 10 m/s²)
  22. A body moving at 3 m/s accelerates uniformly at 6 m/s² for 9 s. What is its final speed?
  23. What force gives a mass of 17 kg an acceleration of 2 m/s²?
  24. What is the kinetic energy of a 4 kg body moving at 3 m/s?
  25. How much gravitational potential energy does a 2 kg mass gain when lifted 16 m? (take g = 10 m/s²)
  26. A force of 20 N acts at 60° to the horizontal and moves a body 3 m along the horizontal. How much work does it do?
  27. A force of 1000 N acts on an area of 0.5 m². What pressure does it exert?
  28. What is the pressure due to a column of liquid of density 1030 kg/m³ and depth 10 m? (take g = 10 m/s²)
  29. A spring of constant 400 N/m is stretched by 0.3 m. How much energy is stored in it?
  30. A resistor of 20 Ω carries a current of 3 A. What is the potential difference across it?
  31. How much energy in kWh does a 2000 W heater use in 3 hours?
  32. A 5 μF capacitor is charged to 10 V. How much charge does it store?
  33. A transformer has 200 turns on the primary coil and 2000 turns on the secondary. The primary voltage is 110 V. What is the secondary voltage?
  34. How much heat is needed to warm 2 kg of water by 20 °C? (specific heat capacity of water = 4200 J/(kg °C))
  35. A radioactive sample of 640 g has a half-life of 3 days. How much remains after 9 days?
  36. A body moving at 12 m/s accelerates uniformly at 5 m/s² for 4 s. What is its final speed?
  37. What force gives a mass of 14 kg an acceleration of 5 m/s²?
  38. What is the kinetic energy of a 5 kg body moving at 15 m/s?
  39. How much gravitational potential energy does a 5 kg mass gain when lifted 27 m? (take g = 10 m/s²)
  40. A force of 20 N acts at 60° to the horizontal and moves a body 10 m along the horizontal. How much work does it do?
  41. A machine does 1200 J of work in 20 s. What is its power?
  42. What is the pressure due to a column of liquid of density 1000 kg/m³ and depth 10 m? (take g = 10 m/s²)
  43. A source vibrates with a frequency of 10 Hz. What is its period?
  44. A device on a 12 V supply draws 0.5 A. What is its power?
  45. A wire 2 m long carries 10 A at right angles to a magnetic field of 0.2 T. What force acts on it?
  46. A transformer has 200 turns on the primary coil and 2000 turns on the secondary. The primary voltage is 220 V. What is the secondary voltage?
  47. A gas in a rigid container is at 300 kPa and 250 K. Its temperature is changed to 375 K. What is the new pressure?
  48. A radioactive sample of 80 g has a half-life of 2 days. How much remains after 6 days?
  49. A body of volume 0.002 m³ is fully immersed in a liquid of density 800 kg/m³. What is the upthrust? (take g = 10 m/s²)
  50. A body moving at 4 m/s accelerates uniformly at 5 m/s² for 6 s. What is its final speed?

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